1. Field of Invention
The invention relates to a removable intravascular filter system used in connection with intravascular medical procedures, the purpose of which is to prevent solid material from being released into the vascular system.
2. Description of Related Art
U.S. Pat. No. 5,941,896 reports that advances in medicine and technology are leading to the development of minimally invasive surgical techniques for treatment of various medical conditions. For example, stenosis formed in a blood vessel may be treated endovascularly using techniques such as balloon angioplasty, stent placement, or thrombolysis. However, the use of such endovascular techniques has been limited due to embolization of debris from the treated portion of the vessel to a downstream portion resulting in complications. For example, treatment of a stenosis in a carotid artery can result in ischemic complications and possible embolic stroke.
International Publication WO 99/44510 discloses a guidewire filter which has an elongate hollow tube with a proximal end, a distal end, an inside and an outside surface, and a lumen formed throughout. The hollow tube has a plurality of longitudinal slots forming a plurality of longitudinal rib portions near the distal region of the hollow tube. An actuating wire with a proximal end and a distal end is provided and is xe2x80x9cpermanently attachedxe2x80x9d to the distal end of the guidewire filter. Filter material is positioned within the lumen in the hollow tube. An activation handle on the proximal end of the device is provided for pulling the actuating wire relative to the hollow tube. An object of the invention is to provide for a guidewire filter in which the filter is deployed by xe2x80x9cpullingxe2x80x9d rather than by pushing on an actuating wire allowing use of a thinner wire; although, optionally, the hollow tube can be pushed relative to the actuating wire to deploy the filter. The actuating wire is taught to be only as thick as possible to carry the force required to activate the filter assembly yet to provide as much room as possible for the filter material to fit inside the outer hollow tube. A disadvantage of this technology is that the actuating wire is permanently attached to the guidewire filter and must remain in place during the entire procedure, subjecting the artery to a possibly too rigid two layer guidewire.
International Publication WO 00/16705 discloses a removable vascular filter system for blocking micro and macro emboli while allowing continual blood circulation. The device comprises a guidewire and a filter assembly which is attached to the guidewire at the guidewire""s distal end. A movable core wire is attached to the filter assembly to actuate it. Attachment of the filter membrane to the guidewire is taught to allow expansion of the filter membrane with a firm fit inside the artery and to allow for collapse of the membrane tightly through the guidewire. The guidewire is used for the entire procedure from crossing a lesion to deploying a stent. Embodiments of the invention include a filter membrane consisting of a thin membrane attached to the guidewire and supported by metal spines. Another embodiment comprises a filter membrane which rests upon or is attached to a basket-like structure, which is attached to a guidewire at one end. Yet another embodiment uses a retractable sheath at the distal end of the guidewire which covers the filter membrane in the collapsed state. The sheath distal portion is affixed to the guidewire tip, which is affixed to the distal end of the movable core and is taught to prevent the filter membrane from becoming entangled in an artery or guide catheter.
A disadvantage of an external sheath design is that it increases the diameter of the filter system in a patient""s arteries, which is especially important with the sheath going over an arterial lesion before and after a medical procedure. In the device of WO 00/16705, the filter membrane must be affixed at least at its distal portion to the core wire and/or basket wire distal ends.
International Publication WO 99/23976 discloses an embolic protection device comprising a collapsible filter element which is slidably mounted on a guidewire for axial movement along the guidewire. The device is equipped with stoppers to limit axial movement along the guidewire. The filter element collapses into the outer end of a catheter for deployment and retrieval through the vascular system of a patient. The filter element has a collapsible filter body with a proximal inlet end and a distal outlet end. After use, the catheter is movable along the guidewire to engage the proximal end of the filter element and to close the inlet openings before sliding over the filter element from the proximal end to the distal end to progressively collapse the filter body on the guidewire for retrieval. The catheter acts as a sheath to protect the vessel walls during deployment and retrieval of the filter element. The filter element is attached to a shaft that can run over the primary guidewire and that is attached on one portion of the filter element. Moreover, filter membrane designs are taught which reduce the longitudinal length of creases which may occur should the filter be oversized, acting as crease breakers. Membrane designs are also taught which include a series of channels or pathways.
This design also relies on the use of sheaths which add to the rigidity of the device in the patient""s arteries and add to the radial dimension and size of the device.
U.S. Pat. No. 6,142,987 to Tsugita et al. discloses a guided filter system for temporary placement of a filter in an artery or vein. The system includes a guidewire slideable through a wire guide included at a distal region of a support wire. The support wire has an expandable filter, which is operable between a collapsed and an enlarged condition and is attached to the support wire. A variety of endovascular devices, including angioplasty, artherectomy, and stent deployment catheters, are insertable over the guidewire and/or the support wire. Various embodiments of the invention include an expandable filter which is mounted at the distal region of the support wire, as well as capture sheaths. Methods of using the guided filter system to direct and exchange endovascular devices to a region of interest, and to entrap and remove embolic material from the vessel are also disclosed.
U.S. Pat. No. 5,941,986 to Kerr discloses a filter and method for trapping emboli during endovascular procedures. In one embodiment, the filter is formed from a bent, flexible guidewire shaped to define a frame and a porous filtering. material attached to portions thereof. In a collapsed state, the filter can readily pass through the lumen of a catheter and into the bloodstream of a patient. Upon completion of an endovascular procedure, the filter is collapsed and retracted into the catheter. In alternative embodiments of the invention, porous filtering material is mounted to external portions of a catheter, and a control guidewire is attached to the filtering material to selectively control the filter between the open and closed states.
International Publication WO 96/01591, by Mazzochi et al. discloses a vascular trap comprising an umbrella-shaped basket carried adjacent a distal end of a guidewire. The guidewire includes a tapered distal section with a spirally wound coil basket extending along a distal length of the wire. The basket is positioned generally distally of the coil and is preferably attached to the guidewire proximal of the proximal end of the tapered section. The basket may be attached by means of tethers which are attached to the guidewire by means of metal straps. The basket may be closed by pulling the guidewire into a sheathing catheter.
U.S. Pat. No. 6,027,520 to Tsugita et al. discloses an apparatus and method for preventing detachment of mobile aortic plaque within the ascending aorta, the aortic arch, or the carotid arteries, and to an apparatus and method for providing a stent and a filter in a percutaneous catheter for treating occlusions within the carotid arteries. The embodiments of this invention have a plurality of struts which are attached at a distal end of the guidewire and extend distally. The struts are connected to each other at each end and have an intermediate region which is biased to expand radially. The filter mesh is attached between the intermediate region and the distal end of the struts. In other embodiments the struts are attached to the distal end of the sheath. The struts extend distally from the sheath and attach to the distal end of the guidewire. Embodiments also include a filter mesh attached to struts between an intermediate region and distal end of the guidewire.
Embodiments of the invention provide a removable filter system with a simple actuating mechanism of few parts.
Embodiments of the invention provide a removable filter system which can be used in the blood vessels of a patient without the need for a sheath covering the filter.
Embodiments of the invention provide a filter system with the ability to select the rigidity of an actuating wire during positioning or deployment of the filter system and use of the guidewire.
Embodiments of the invention provide a removable filter system which can be deployed without the filter membrane being permanently fixed or attached to the actuating wire.
Embodiments of the invention provide a self-contained, removable filter system that has a slender diameter and presents a reduced risk of dislodging embolic material during positioning.
Embodiments of the invention provide a removable filter system that allows deployment of a filter assembly comprising a filter membrane which is biased in either the closed or the open position. An actuating wire is inserted through the proximal end of the filter assembly and engages the filter assembly to deploy or collapse the filter assembly.
Embodiments of the invention provide a filter system comprising a filter assembly which has a distal and a proximal end, a hollow guidewire which is connected to the proximal end of the filter assembly, and an actuating wire which is longitudinally movable through the lumen of the hollow guidewire but not affixed to the filter assembly. The actuating wire is engageable with the filter assembly at the filter assembly""s distal end.
Embodiments of the invention provide an intravascular filter with distinctive shapes that reduce the clogging effect due to trapped emboli.
Embodiments of the invention provide a control device to prevent unwanted displacement of the actuating wire.
Embodiments of the invention provide a control mechanism for operating the actuating wire with a locking mechanism which allows a pre-defined movement of the actuating wire and prevents damage to the filter.
In embodiments where the filter system is biased open, the actuating wire may be advanced beyond the distal end of the hollow guidewire and engage the distal end of the filter assembly, collapsing the filter assembly to the closed position during movement through a vessel. The filter assembly deploys to the open position against a vessel wall upon retraction of the actuating wire. The actuating wire may optionally be entirely removed while the filter system is deployed or replaced with a wire of different rigidity. The filter system may be easily closed and readied for removal from a patient""s circulation upon advancing of the actuating wire into the distal end of the filter system.
In embodiments where the filter assembly is biased closed, the distal end of the actuating wire may convert to any desirable three-dimensional configuration upon being advanced beyond the distal end of the hollow guidewire. The actuating wire then removably engages the filter assembly, deploying the filter assembly in the open position against the vessel wall. The actuating wire is easily retracted into the hollow guidewire so that the filter assembly closes for removal from a patient""s circulation. Thus, the actuating wire may even be absent or replaced with an actuating wire of different rigidity during placement or removal of the hollow guidewire.
In embodiments, the present invention provides an intravascular filter having a cage which is supported by a plurality of ribs extending from the proximal end to the distal end of the cage. The ribs are constrained against radial movement to a vessel wall at the distal end of the cage. The ribs are radially movable into contact with the vessel wall, however, at the proximal end of the cage. A filter membrane is supported within the cage and includes a proximal portion that contains radial convexities extending radially outward between the ribs to contact the vessel wall when the filter is deployed.
In embodiments, the present invention provides an intravascular filter which contains a filter membrane which has a distal portion that includes radially extending concavities that extend inward between the ribs to assist in controlled folding of the intravascular filter for positioning or removal.
In embodiments, the present invention also provides an intravascular filter which has a filter membrane which when deployed has a proximal portion that is axially convex and a distal portion that is frustoconical or tubular and of a smaller diameter than the proximal portion.
In embodiments, the present invention provides for a device for controlling movement of an actuating wire through a lumen of a hollow guidewire, comprising a first, axially constrained gripper configured to grip a proximal portion a hollow guidewire, a second axially movable gripper configured to grip a portion of the actuating wire extending out of the proximal portion of the hollow guidewire, and a control member for moving the axially movable gripper over a predetermined axial distance.
In embodiments, the present invention provides for an intravascular filter system comprising a hollow guidewire which has an axially extending lumen, an actuating wire which extends through the lumen, a filter assembly that can be deployed or collapsed by the actuating wire, and a control mechanism. The control mechanism controls the extent of axial movement of the actuating wire through the lumen of the guidewire. The control mechanism has at least one projection on either an interior surface of the guidewire or an exterior surface of the actuating wire. In addition, the control mechanism has at least one indentation, such as a groove, for mating on either of the guidewire or the actuating wire.
In embodiments, the present invention provides a filter assembly, having a filter membrane made of a single sheet of material which can be folded or otherwise shaped mechanically to form the desired filter shape.
In embodiments, the present invention provides a filter assembly, having a filter membrane composed of polymeric material with laser cut holes or a single sheet of metal such as Nitinol(copyright) in which the membrane portion has laser cut holes.
In embodiments, the present invention provides a method of trapping and removing solid material from a vessel of a patient, using filter systems of the type described herein.